Drought is an important abiotic stress factor limiting crop productivity worldwide and its impact is increasing with climate change. Regardless of the plant growth period, drought has a deadly and yield-reducing effect on the plant at every stage of development. As with many environmental stressors, drought-exposed plants trigger a series of molecular, biochemical, and physiological responses to overcome the effect of drought stress. Currently, researchers are trying to determine the complex functioning of drought stress response in plants with different approaches. Plants are more sensitive to drought stress during certain critical stages like germination, seedling formation, flowering, fertilization, and grain formation periods. Plants have high success in reducing the effects of drought stress in vegetative development periods with the activity of tolerance mechanisms. On the other hand, drought stress during the generative period can cause irreversible losses in yield. This review focuses on the progression of molecular, biochemical, and physiological mechanisms involved in the drought stress tolerance in plants and the responses of field crops to drought stress at different development stages.

Salt stress is one of the harmful abiotic stress factors. It makes agricultural lands especially in arid and semi-arid regions useless despite the efforts. More than six percent of total world agricultural lands are on the edge of vanishing due to salt stress. Salinity in soil occurs as a result of the factors such as lack of drainage, improper irrigation, excessive accumulation of soluble salts. Salinity limits the growth of plants. Despite the main results, some results of plants due to these limitations vary from species to species. The negative effects get morphological, biochemical and physiological reactions from plants. Slowed or stopped growth of roots and shoots, closuring of stomata, germination slowing, decreased or stopped development of seedling, deterioration of photosynthetic activity are the main reactions of plants to stress. On the other hand, plants also develop tolerance mechanisms as a result of some auxiliaries for surviving under adverse conditions. Plants have tendency to protect themselves from salinity with osmotic protectants synthesized by them such as sugars, proline, amino acids, glycine betaine. In this review, the responses of plants to salt stress were investigated and gathered.

Salinity is an abiotic stress factor that reduces yield and threatens food security in the world’s arid and semi-arid regions. The development of salt-tolerant genotypes is critical for mitigating yield losses, and this journey begins with the identification of sensitive and tolerant plants. Numerous physiologic and molecular markers for detecting salt-tolerant wheat genotypes have been developed. One of them is proline, which has been used for a long time but has received little information about proline-related genes in wheat genotypes. In this study, proline content and the expression levels of proline-related genes (TaPTF1, TaDHN, TaSRG, TaSC, TaPIMP1, TaMIP, TaHKT1;4, TaGSK, TaP5CS, and TaMYB) were examined in sensitive, moderate, and tolerant genotypes under salt stress (0, 50, 150, and 250 mM NaCl) for 0, 12, and 24 h. Our results show that salt stress increased the proline content in all genotypes, but it was found higher in salt-tolerant genotypes than in moderate and sensitive genotypes. The salinity stress increased gene expression levels in salt-tolerant and moderate genotypes. While salt-stress exposure for 12 and 24 h had a substantial effect on gene expression in wheat, TaPTF1, TaPIMP1, TaMIP, TaHKT1;4, and TaMYB genes were considerably upregulated in 24 h. The salt-tolerant genotypes showed a higher positive interaction than a negative interaction. The TaPTF1, TaP5CS, TaGSK1, and TaSRG genes were found to be more selective than the other analyzed genes under salt-stress conditions. Despite each gene’s specific function, increasing proline biosynthesis functioned as a common mechanism for separating salt tolerance from sensitivity.

The aim of this study was to compare seed germination percentage, seedling growth, total chlorophyll and protein content, sugar content, and root and sugar yields of sugar beet (Beta vulgaris L.) genotypes at different ploidy levels. Sugar beet seeds from cultivars “Agnessa” and “Felicita” (diploids), and lines “AD 440” and “CBM 315” (tetraploids) were obtained from the Sugar Research Institute, Etimesgut, Ankara. Seed germination percentage was recorded after 4 days, whereas seedling and root lengths were noted 4 and 14 days after the study initiation. The size of epidermal cells in length and width were determined on the upper leaf surface of 6-week-old plants. Six and 10 weeks after seed sowing, plant and root lengths, leaf length and width, plant fresh and dry weights, and total chlorophyll and protein content were measured. Data related to yield components such as sugar content, root and sugar yields were obtained from trials conducted by the Sugar Research Institute under field conditions 6 months after study initiation. In the current study, diploid genotypes showed superior responses regarding generative characteristics while tetraploids passed diploid ones vegetatively in the further stages of the development. Ten weeks after study initiation, the highest results regarding vegetative characters such as plant height, root and leaf lengths, leaf width, approximate leaf area, plant fresh and dry weights, and tissue water content were recorded from tetraploid genotypes as 35.00 cm, 43.85 cm, 18.40 cm, 9.25 cm, 170.35 cm², 369.10 g, 77.45 g and 291.65 g, respectively while the highest total chlorophyll content and protein percentage was obtained from diploid genotypes as 1552.65 μg g^–1 fresh tissue and 21.11%, respectively. The highest values of sugar content, root and sugar yields were obtained from diploid genotypes as 15.55%, 71.47 t ha^–1 and 11.09 t ha^–1, respectively.